This looks like it fits my bill for a decent, light laptop for under £500.
To get this price you need to get £30 off for new customer code, it seems to just need an email address though so shouldn't be difficult to get. And then they take 10% (£47) off at checkout; hope that makes sense. (Probably no cash back as using code but there's 3.15% at TCB if you want to try.)
Looks like it's £500 or more elsewhere. Also AO.com have 50% off on Office 365 - so can you can add it for £39.99 here which I think is reasonable.
Please let us know if there are better alternatives at this sort of price.